The SSA wants you to work. They want you to support yourself so they don't have to. (That may be blunt, but it's the truth.)
It's kind of like the welfare "Ticket to Work" program.
Yes, you're disabled and can't work, so you are approved. If you're working, then you will not be approved. However, once you ARE approved they want to try and get you off the "rolls" if at all possible.
You are allowed to work and earn a certain amount when you're on SSD or SSI. (Except for your 9 month "trial work period" where there are no income limits and you can continue to receive your full benefits.) If you work at less than the SGA level ($810 per month) then it's assumed that your disability still exists and that's the reason why you can't make substantial money. However, if you work and earn more than the SGA, then that basically says your disability isn't affecting you anymore, therefore they will label you as no longer disabled.
It's not they're contradictory to one another, it's that the SSA would like to see you be able to work and they give you incentives to do that. Being able to work only 2 days a week to earn a little bit of money to supplement the SSI or SSD payment doesn't mean that you're not disabled still. It just means that you're trying to get by. The most a person can get from SSI is $564 a month. That's it. Now, a persons past earnings is what determines how much SSD they'll get every month. But, if they get over the $564 in SSD a month, then they don't qualify for SSI (for example: A person's earnings entitle them to $1500 a month in SSD They wouldn't get SSI because they already get more than what SSI would pay in the first place). In my case, my SSD is only $364 a month or so. I qualify for $200 a month SSI to bring me up to that $564 a month level. It's not really possible to survive on $564 a month. If I find that I'm able to work a couple of days a week to supplement that, then I'm not penalized for "trying" because 2 days of work a week isn't SGA level, and I may not even be able to work those 2 days a week for very long. Now, if I'm working 40 hours a week, that's considered SGA.
I think I just confused myself even more. LOL